We often run into cases where an IVR (interactive voice response) system may not generate shipment orders for study kits every day. For example, commonly it seems they may only ship Monday through Thursday. In many cases this could be due to cold chain supplies having to be received immediately and being unable to guarantee that someone will be there to receive the shipment on a weekend. Others, however, may be for unrelated policy reasons. Standard modeling practice says to add a day to the shipping lead-time for every day that is not available for shipping (3 days in the case of the above example). Related to this concept, there is often some confusion for new users about whether the shipping lead-time for the IVR study refers to calendar days or business days.